CONVECTIVE FORECAST
VALID 06Z SUN 07/12 - 06Z MON 08/12 2003
ISSUED: 06/12 17:20Z
FORECASTER: DAHL

General thunderstorms are forecast across the Ionian Sea ... Greece ... Aegean Sea.

SYNOPSIS

Vigorous upper trough ATTM over east-central Europe is rapidly digging south. Its southern tip is expected to become separated from the main trough as vort max ATTM over the Baltic Sea continues its southern track while main vort max associated with intense SFC low moves ENE ... which will eventually result in an upper cut-off low over the central Mediterranean towards the end of the FCST period. Cold front associated with the upper trough is expected to curve from the Tyrrhenian Sea across the S Balkan States and the Aegean Sea northeastwards into Russia at the beginning of the FCST period. Models assume pressure falls ahead of ... and late Sunday night also along the cold front over the Ionian Sea ... Greece and the Aegean Sea. Otherwise ... large north-Atlantic upper ridge will spread across Europe ... resulting in an omega-type flow pattern by Monday morning with a large SFC high centered over central Europe.

DISCUSSION

...Northern Mediterranean ... Italy ... W Mediterranean...
Strong vort max will move into the central Mediterranean during the day and close off into a cut-off low. Strong elongated maximum of Q-vector convergence is expected to extend along the cold front from the Tyrrhenian Sea into the Black Sea on Sunday 12Z. Weak instability will be a potential problem over southern and central Italy as well as over the adjacent Sea W of Italy. Thinking is that chance of TSTMS along the cold front will be quite low. However ... depending on the intensity of low-level forcing along the cold front ... a line of narrow/shallow convection could form which may produce a few lightning strikes ... later OBS have to be awaited to verify this scenario. It looks that plume of weakly unstable airmass associated with occluded frontal system ATTM over Iberia ... will be advected into the W Mediterranean ... and eventually reach the cold front. PRIND that unfavorable UVM regime/weakening of the theta-e plume will limit TSTM activity amidst this plume to the very western portions of the Mediterranean and E Spain.

Airmass in the wake of the cold front is quite dry ... and subsidence in the lee of the Dinaric Alps and the Apeninnes along with short residence time of the airmass over the moderately warm sea waters ... should prevent deep cellular convection. ATTM these regions will not be included in a GEN thunder area ... but an updrade could be necessary tomorrow.

...Ionian Sea ... Greece ... Aegean Sea...
CAPE is expected to increase with low-level theta-e advection over the Ionoan/Aegean and (southern) Greece S of the frontal boundary. DCVA will overspread the region ahead of weak southern-stream vort max ATTM over the W Mediterranean Sea. Indications are that elevated TSTMS will develop early Sunday morning over the Ionian Sea ... and spread into Greece and the Aegean Sea during the FCST period. Resonably high chances appear to exist that storms spread as far N as the northern Aegean where very strong theta-e gradient will develop ... GFS assumes 0-3 km SRH to exceed 500 J/kg along the thermal gradient. However ... storms will likely remain elevated as NELY SFC flow will likely be very dry/cold. Farther south over the Aegean ... storms appear to have fair chances of becoming SFC-based. Kinematic setup does not suggest a particularly high supercell threat there ... but a few strong wind gusts and some hail could occur with CAPEs approaching 1000 J/kg and about 40 knots deep-layer shear.

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